Tow brake



Jan. 5, 1960 'w. A. BURN, JR

TOW BRAKE Filed July 28, 1958 2,919,794 Patented Jan. 5, 1960 TOW BRAKEWilliam A. Burn, Jr., Rock Hill, S.C., assignor to Cellanese Corporationof America, New York, N.Y., a corporation of Delaware Application July28, 1958, Serial No. 751,198

8 Claims. (Cl. 20312) The present invention relates to the severing ofcontinuous filament tows to produce staple fiber and more particularlyto the provision of simple and eifective means for braking the tow withsufficient accuracy and rapidity to prevent the tail of the tow frompassing through the staple cutter to thereby permit the tow to besevered into staple at high speed while simultaneously eliminating longcuts in the staple fiber thereby to improve staple uniformity.

In the conventional severing of continuous filament tows to producestaple fiber, it is necessary to brake the tail of the tow to preventthe same from passing through the staple cutters resulting in long cuts.When the tow moves at high speed this braking operation makes itdifficult to achieve high production rates from a single staple cutter.In the past it has been necessary either to cut back production speed byslowing the feed velocity of the tow to the cutter or to toleratelowered staple quality due to the presence of long cuts resulting fromtails passing through the cutter.

In the invention a simple and effective braking system is provided forthe purpose of automatically stopping the tow close to the staple cutterto reduce waste and prior to the passage of the tail through the cutter.In this manner high tow feed velocities are utilized, yet a qualitystaple product is produced.

In accordance with the present invention, the tow is tensioned and thenpassed over a slide member or pin. Means are positioned within the pin,this means being retained within the pin by the tensioned tow. When thetail of the tow is released the tension on the tow drops and the memberpreviously held within the pin by the tensionof the tow is urgedoutwardly either by gravity, spring urging, a weight, or the like. Thetow in its passage to a cutter passes a dragging or further tensioningelement which regulates the velocity of the tow to the staple cutter. Inthe invention, when the member within the pin emerges therefrom uponpassage of the tow tail it actuates means to prevent advance of the tow,e.g. an air-operated clamp which is positioned between the drag elementand the cutter to grasp the tail of the tow before the velocity of thesame can increase which would produce long cuts. The air-operated clampcan be actuated by an air valve, a microswitch, or the like, which isrendered operative when the member within the pin emerges therefrom.

The invention will be more fully understood from the description whichfollows taken in conjunction with the accompanying drawings in which:

Fig. l is a partial perspective view of apparatus constructed inaccordance with the invention;

Fig. 2 is a side elevation of a pin constructed in accordance with theinvention and showing the member which is free for movement when the towend passes the pin to release the tension upon this member and also themicroswitch-operating lever;

Fig. 3 is a cross-section of the pin of Fig. 2 illustrating the actionwhich takes place when the tension supplied by the tow is removed; and

Fig. 4 is a detailed view of the tow clamping means illustrating theclamp, the air piston which operates the same, the solenoid whichactuates the air cylinder and the electrical circuit including themicroswitch which operates the solenoid.

Referring to Fig. 1, a continuous filament tow 10 which is normallysupplied from a drier (not shown) is directed to guide pins 11, 12 and13, the tow 10' passing over the pins 11 and 13 and under the pin 12.Because of the high speed with which the tow is moved and since thedirection of movement of the tow is altered by the pins 11, 12 and 13,the tow presses against the pin 13 until the tail of the tow passes thesame. Accordingly, the instant of time in which the tail passes the pin13 is accurately sensed by the release of tension against the pin.

After passing the guide pins 11, 12 and 13, the tow 10 is bundledtogether as indicated at 14 and is then passed to a drag elementconstituted in the form of the invention which is illustrated by drum 15which is wrapped in the manner illustrated in the drawing. The tensionedtow is then passed to a conventional staple cutter 16 where it is cutinto staple fiber lengths 17.

In accordance with the invention, a clamp 18 is' interposed in the pathof the tow 10- between the staple cutter and the drum 15. The clamp 18is normally open to permit the free passage of the tow therethrough. The

normally open clamp 18 comprises a movable clamp member 19 which isconnected by a shaft 29' to an air cylinder 21. The air cylinder 21 isconnected by means of conduits 22 and 23 and an intervening normallyclosed valve 24 to a source of fluid under pressure.

The pin 13 is provided with means for sensing the release of tensionapplied by the tow in its passage over the pin. This sensing means isinterposed in a longitudinal channel 25 and operates to open the valve24 and permit air to pass through the conduit 22 to close the clamp 18.

Operation of the sensing means in the channel 25 and of the clamp 18will be described more fully hereinafter.

At this point it is desired to emphasize that the invention relies uponan accurate sensing of the passage of the tail of the tow over a givenpoint up stream from the cutter in order to operate a clamp adjacent thecutter in time to grasp the tail of the tow so that this tail isprevented from passing through the staple cutter to improve theuniformity of the staple product which is produced while at the sametime reducing waste represented by the uncut tail portion of the tow toa minimum. To this end the time interval between movement of the sensingmeans out of the position shown in Fig. 2 and clamping of the tow end iscorrelated to the distance between the sensing means and clamp so thatthe length of-the tow between the clamp and dragging or tensio-ningelement will be a minimum.

The staple cutter 16 which is used is of conventional type and is notshown in detail in the drawing. It is sufficient to point out that thelength of the staple is governed by the velocity of the tow. When thetail of the tow passes the drum 15, the frictional drag is eliminatedand the velocity of the tow increases so that the staple cutter producesstaple of excessive length, e.g. long cuts are produced. The inventionby clamping the tow between the staple cutter and the mechanism employedto create a frictional drag upon the tow causes the tow to be caughtbefore its speed has increased unduly.

The sensing mechanism of the invention is more clearly shown in Figs. 2and 3 where it will be seen that a lever 26 is mounted in the channel25, the lever 26 being pivoted at 27 for movement into and out of thechannel 3 25. In the preferred construction illustrated, the lever 26comprises an arm 28 which fits within the channel 25 and an extension 29which bears against a sensing arm 30 operatively connected with valve24.

As will be evident in Figs. 2 and 3, the pin 13 is formed with acylindrical bore 31 which receives a compression spring 32. When the arm28 of the lever 26 is forced into the channel 25 by the tension of thetow (this tension created by the undulating path of the tow effected bythe combination of pins ll, 12 and 13) the spring 31 is compressedwithin the bore 31. As soon as the tow tail passes the pin 13, thetension on the arm 28 is relieved and the pin 13 ejects the arm 28 fromthe channel 25 as indicated in phantom in Fig. 3. As a result, extension29 displaces sensing arm 30 to open valve 24.

Preferably the opening of valve 24 is effected by direct mechanicalconnection of this valve with sensing arm 3t). Alternatively, it can beeffected electromechanically as illustrated in Fig. 4. The sensing arm3% (not shown) controls a rnicroswitch 33 which is interposed in anelectrical circuit in series with the armature of a solenoid 34. Theelectrical circuit may include a manual switch 35 which is closed toactivate the electrical circuit.

As can be seen in Fig. 4, and assuming the manual switch 35 to beclosed, operation of the microswitch 33 draws the core 36 of thesolenoid upwardly within the solenoid to open the valve 24 and tothereby permit air to pass from a supply thereof through the conduits 23and 22 to the air cylinder 21. As will be evident, the application ofair pressure to the cylinder 21 will move the shaft 20 forwardly toforce the movable platen 19 against the stationary platen 37 of theclamp 18.

In the construction of Fig. 4, a guide 38 is welded to the clamp support39 to facilitate threading of a fresh tow through the clamp 18. Theclamp support 39 is formed with a depending flange 40 which is formedwith openings 41 to facilitate securement of the clamp structure to thesupport means which carry the drum 15 and its associated guides.

The details of construction of the valve 24 and the air cylinder 21 aswell as the conduits which interconnect the same to permit projectionand retraction of the shaft 20 have not been discussed as these areconventional.

Referring to Figs. 1, 2 and 3, the pins 11, 12 and 13 are mounted upon aplate 42 (see Fig. 1), these pins being secured to a support positionbehind the plate 42 as by the threaded extensions 43. It will beobserved that the extension 29 of the lever 26 extends through a slot 44in the plate 42, the sensing arm 30 being positioned behind the plate 42and hence not seen in Fig. 1.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of my invention.

Having described my invention what I desire to secure by Letters Patentis:

1. Apparatus for severing continuous filament tows at high speed toproduce staple fiber comprising a staple cutter for severing said tow,means for placing said tow under tension while moving to said cutter,means for sensing an end of said tow before said end reaches saidtensioning means, and means for preventing advance of said tow, saidadvance preventing means being disposed intermediate said tensioningmeans and said cutter, said sensing means and said advance preventingmeans being operatively connected, whereby when an end of said tow 41 issensed by said sensing means said advance preventing means is actuatedand advance of said tow is prevented with the end between saidtensioning means and said cutter thereby to prevent said end frompassing to said cutter.

2. Apparatus as recited in claim 1 in which the time interval betweensensing of said tow end and the time when advance of said tow isprevented is correlated to the distance between said sensing means andsaid advance preventing means so that the length of tow from saidadvance preventing means to said tow end is a minimum.

3. Apparatus for severing continuous filament tows at high speed toproduce staple fiber comprising a staple cutter for severing said tow,spaced first and second means for placing said tow under tension whileadvancing to said cutter, means for sensing an end of said tow betweensaid first and second tensioning means, means for clamping said towdisposed intermediate said second tensioning means and said cutter, saidsensing means and said clamping means being operatively connected,whereby when an end of said tow is sensed by said sensing means saidclamping means is actuated and advance of said tow is prevented with theend between said second tensioning means and said clamping means therebyto prevent said end from passing to said cutter.

4. Apparatus for severing continuous filament tows at high speed toproduce staple fiber comprising a staple cutter for severing said tow,means for placing said tow under tension while advancing to said cutter,sensing means urged into a first position, said sensing means contactingsaid tow and being maintained in a second position by the tension onsaid tow, and clamping means including a displaceable member normallyspaced from said tow and disposed intermediate said sensing means andsaid cutter, said sensing means and said member being operativelyconnected, whereby when an end of said tow passes said sensing meanssaid sensing means moves from its second position into its firstposition 7 thereby to actuate and displace said member to clamp said towand prevent said end from passing to said cutter.

5. Apparatus as recited in claim 4 in which said clamping means includesa stationary platen toward which said member moves to clamp said towtherebetween.

6. Apparatus as recited in claim 4 in which said sensing means includesa pin formed with a longitudinal channel and said portion of saidsensing means includes a lever pivotally mounted within said channel,said sensing means further including an extension arm movable with saidlever and projecting from said channel at a point spaced laterally fromthe path of said tow, resilient means for ejecting said lever from saidchannel in the absence of tension from said tow, and a sensing armpositioned in the path of said extension arm operatively connected withsaid clamping means.

7. Apparatus as recited in claim 4 including a plurality of horizontallyoffset pins about which said tow passes before contacting said sensingmeans, thereby being placed under tension.

8. Apparatus as recited in claim 4 in which the operative connectionbetween said sensing means and said member includes an air cylinderconnected to said member, air supply means connected to said aircylinder, and a valve controlling said air supply means.

No references cited.

